Internal sealing means for autoclave motor housing



June 25, 1968 K. FITZPATRICK 3,389,973

INTERNAL SEALING MEANS FOR AUTOCLAVE MOTOR HOUSING Filed June 23, 1967FIQQRE Q KERIEN FITZPATRICK FIGURE l INVENTOR.

BYW

ATTORNEY United States Patent 3,389,973 INTERNAL SEALING MEANS FORAUTOCLAVE MOTOR HOUSING Kerien Fitzpatrick, Odessa, Tern, assignor tolgexall Drug and Chemical Company, Los Angeles, Callf., a corporation ofDelaware Filed June 23, 1967, Ser. No. 643,290 4 Claims. (Cl. 23-290)ABSTRACT OF THE DISCLQSURE Sealing means between reaction and agitatormotor sections comprises disc having peripheral grooves containingresilient and expander rings with clearance provided for fluid passage'to spaces between grooves and expander rings whereby fluid pressurefrom reaction section urges resilient rings against autoclaves wallpreventing passage of fluid to motor section.

BACKGROUND OF INVENTION (1) Field of invention This invention relates toa combination of an autoclave and means for sealing 01? an internalmotor section from fluid from the reactor section of the autoclave. Theterm autoclave used herein refers to a pressure vessel comprising ashell and a head generally operating at high pressures, i.e., 100 to15,000 atmospheres.

(2) Description of prior art The prior art autoclaves found in theprocessing industry are cylindrical or spherical and are positionedeither vertically or horizontally, and have :at least one flat, dishedor semihemispherical head. The autoclave most commonly found in industryin high pressure service is a vertical, substantially cylindrical typeof vessel having a removable top head and an agitator, or other meansforstirring the contents of the autoclave, extending through or from thetop head and along the longitudinal axis of the autoclave.

Such vessels have found wide acceptance as reactors for either batch orcontinuous reactions. For example, it is well known to polymerizeethylene in an autoclave at pressures ranging from 15,000 psi. or belowto 45,000 psi. and higher and at temperatures of about 200 to 600 F. inthe presence of a free radical initiator. Such polymerization reactionsrequire vigorous agitation to provide intimate contact between the feedand the contents of the autoclave. The autoclave is provided with anagitator or other means for mixing its contents and a motor or othermeans for driving the agitator. The agitator motor within its housing isusually mounted on the exterior surface of the autoclave (see US. PatentNos. 2,897,183, and 2,964,515). The entire motor housing has beenenclosed within the interior of the autoclave. Heretofore, this has notbeen too successful because no sealing devices have been available inthe industry which completely seal oif the internal motor and housingfrom fluids in the reaction section. The sealing devices of the priorart allow reactants from the reaction section of an autoclave to passinto the space between the exterior of the motor housing and theinterior of the autoclave. The reactants polymerize and accumulate inthis space making removal of the motor housing difficult. Thepolymerized reactants even Work their way into the motor windingsimpairing the performance of the motor.

SUMMARY An object of the present invention is to prevent fluid from thereaction section of a stirred autoclave from back flowing into the drivemeans section of the agitator.

Another object of the present invention is to provide 3,389,973 PatentedJune 25, 1968 an apparatus combination including a sealing means forcompletely sealing off the internal agitator motor from fluids in thereaction section.

The present invention comprises in combination: an autoclave having areaction section, an agitator extending along the longitudinal axis ofthe autoclave, means for driving the agitator positioned within a drivemeans section above the reaction section and sealing means forpreventing back-flow of fluid into the drive means section. This sealingmeans comprises a disc positioned between the reaction section and thedrive means section and a resilient ring and an expander ring seatedbetween the sidewalls of a groove encircling the periphery of the disc.The diameter of the disc is substantially equal to the inside diameterof'the autoclave and is preferably normal to the longitudinal axis ofthe autoclave. The peripheral encircling groove of the disc is generallyrectangular in cross section. The outer periphery of the resilient ringabuts the inner wall of the autoclave and the outer periphery of theexpander ring abuts the inner periphery of the resilient ring. Anannular space is formed between the inner periphery of the expander ringand the inner surface of the groove. Sufiicient clearance is providedbetween the sidewalls of the groove and the respective edges of theresilient and expander rings to permit the passage of fluid from thereaction section to the annular space. Means are provided for pressuringthe autoclave whereby fluid pressure transmitted from the reactionsection via the clearance and the annular space urges the resilient ringagainst the inner Wall of the autoclave to effect a sealing. contactbetween the outer periphery of the resilient ring and the inner wall.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be morereadily understood and the future objects and advantages thereto will bemore readily apparent when read in conjunction with the accompanyingdrawings in which:

FIG. 1 is a vie-w, partially in cross section, showing the autoclave,agitator, internal motor and sealing means;

FIG. 2 is an enlarged detailed view taken along line A-A of the sealingmeans;

FIG. 3 is a view of the transverse section taken along line BB of thesealing means set within the shell of the autoclave.

PREFERRED EMBODIMENT OF THIS INVENTION In the preferred embodiment ofthis invention there is provided a substantially cylindrical, verticallyelongated autoclave having a removable top head, a motor section belowthe top head and a reactor section immediately below the motor section;an agitator extending along the longitudinal axis of the autoclave; anagitator motor Within a housing positioned in the motor section; asealing ring comprising a disc having a plurality of peripheralencircling grooves and a plurality of resilient rings and expander ringseach positioned as indicated under the Summary section; and means forpressuring the autoclave whereby fluid pressure is transmitted from thereaction section via the clearance provided between the sidewalls of atleast the lowermost groove closest to the reaction section and the loweredges of at least the lowermost resilient and expander rings and via atleast the lowermost annular space. The pressure urges at least thelowermost resilient ring vertically upward against the upper sidewall ofat least the lowermost groove and urges at least the lowermost resilientring radially outward against the inner wall of the autoclave normal toits surf-ace to effect sealing contact between the outer periphery of atleast the lowermost resilient ring and the inner wall. The exact paththe fluid that exerts the pressure takes is not fully understood.Whether the fluid actually fills the annular space and forces theexpander ring against the resilient ring which is forced, in turn,against the inner wall or whether the fluid works between the expanderring and resilient ring and forces the latter directly against the innerwall is not critical so long as the net eifect is the same.

Resilient and expander rings in the grooves above the lowermost groovesare providedas a precaution to assure that none of the fluid from thereaction section passes through this plurality of rings and into spacebetween the motor housing and the inner surface of the motor section. Itis understood that any fluid that passes above the lowermost resilientring follows a path within each of the grooves similar to that taken bythe fluid in the lowermost groove.

Referring now to FIG. 1, autoclave 1 comprises metal shell 2 having aninside diameter (ID) of several inches and removable top head 3 which isheld into position by at least one clamp 4 or other suitable means.Autoclave 1 can be provided With a bottom head and clamp (not shown)similar to that shown in FIG. 1 or with a bottom heat that is integralto the shell. Autoclave 1 can also be provided with an external jacketor other means (not shown) for heating or cooling its contents. If theautoclave is used for carrying out continuous reactions, suitable inletsand outlets (not shown) are provided for feed, initiator and efiiulent.Agitator shaft 6 extends through substantially the entire length ofreaction section of autoclave 1. Agitator blade members 7 which are bentinto spiral or helical configuration or other suitable means for mixingthe centents in the reaction section are disposed along the length ofshaft 6. Internal electric motor 8 within motor housing 8A or othersuitable drive means for the agitator is operably connected to shaft 6and is disposed in motor section 9 above reaction section 5. Internalsealing ring 10 is mounted below motor section 9 and above reactionsection 5 to prevent fluid from backfiowing from reaction section 5 intomotor section 9 and accumulating in the annular space between motorhousing 8A and the inner walls of motor section 9.

Sealing ring 10, as shown in FIGS. 1, 2 and 3, comprises disc 11 whichhas an outside diameter about Ai-inch less the ID. of shell 2 and hasthree peripheral encircling grooves 12, Grooves 12 have a rectangularcross section about %-inch wide and about /4-inch high. Seated withinthe outer portion of each groove 12 adjacent the inner wall of shell 2is resilient ring 13 which has an CD. of about pi -inch greater than theID. of shell 2 and has a square cross section of about /4-inch.Resilient rings 13 are formed of heat-resistant rubber, plastic orsimilar material which has high elasticity and is compressible onsealing engagement with the inner walls of shell 2. Preferably,resilient rings 13 are made of tetrafluoroethylene (TFE) fluorocarbonresins, sold under the trademark Teflon by E. I du Pont de Nemours andCompany. An expander ring 14 about As-inch thick and made of metal,preferably stainless steel, is seated within the middle portion of eachgroove 12 abutting respectively each resilient ring 13. Each expanderring 14, of the type commonly found in the compressor art, respectivelyurges each resilient ring 13 radially outward against the inner walls ofshell 2 with sufficient force to effect initial sealing contacttherewith during the period the pressure in the autoclave is increasedto operating pressures. Clearance 15 of about -inch is provided betweenthe lower sidewall of each groove 12 and the lower edges of eachresilient ring 13 and expander ring 14 to allow fluid pressure inreaction section 5 to be transmitted to annular space 16. Space 16 isthe inner portion of groove 12, i.e., the space remaining afterresilient ring 13 and expander ring 14 are seated between the walls ofgroove 12. A A compressor or other means (not shown for pressuringautoclave 1 urges the lowermost resilient ring 13 upward against thesidewall of the lowermost groove 12 and radially outward against theinner wall of shell 2. This effectively .seals motor section 9 againstfluid in reaction section 5 and prevents undesirable reaction to takeplace therein. The sets of resilient and expander rings above thelowermost set are merely provided as a safety factor against possibleleakage into motor section 9.

Disc 11 of sealing ring 10 has a recess to receive the lower portion ofmotor housing 8A. Four countersinks 20 are provided in the outerperiphery of the recess through which four cap screws 21 are passed tofasten sealing ring 10 to motor housing 8A. A bore extends through thecenter of the recess through which agitator shaft 6 passes. Motorhousing 8A is fixedly attached to the inner surface of top head 3 sothat top head 3, motor housing 8A, sealing ring 10 and the agitatorassembly are removable as a unit.

EXAMPLE This example is given to further illustrate the operation of theapparatus of this invention and to indicate the type of process to whichsuch an apparatus is applicable. Ethylene and an organic free radicalinitiator were continuously added through inlets into a reaction sectionof an autoclave of the type shown in FIG. 1. The conditions that weremaintained in the reaction section to convert the ethylene topolyethylene include a pressure in the range of about 18,000 to 30,000psi. and a temperature in the range of about 300 to 600 F. In the motorsection, the pressure was about the same as that in reaction section andthe temperature was less than about 200 F. When the autoclave wasbrought off-stream, the removable unit, comprising the top head, theagitator motor housing, the sealing ring, and the agitator assembly, ofthe type discussed in the above section was removed without difiicultywith no evidence of polymer accumulation in the annular space betweenthe motor housing and the inner walls of the motor section.

A great deal of difiiculty was experienced in removing a removable unitcontaining a sealing ring of the type commonly found in the prior art inplace of the sealing ring of this invention. Accumulations ofpolyethylene were found on the external walls of the motor housing andon the walls of the motor section and some polyethylene was even foundwithin the motor housing in the motor windings. It is theorized that theprior art sealing ring had deformed under the high temperatures and veryhigh pressures used in the autoclave and allowed small amounts ofethylene and initiator to circulate in the motor section. This causedthe temperature in the motor section to rise above the polymerizationtemperature and to cause polymerization.

The essential feature of the present invention is to introduce arelatively simply internal sealing ring into an autoclave to provide aneiiective seal between agitator motor section and the reaction section.

While only one particular embodiment of this invention is illustratedherein, it will be understood that the apparatus of this invention isobviously subject to the variations and modifications without departingfrom its broader aspects. All such variations and modifications thatfall within the scope of the appended claims are intended to be embracedthereby.

What is claimed is:

1. In combination:

(1) an autoclave having a reaction section,

(2) an agitator extending along the longitudinal axis of said autoclave,(3) means for driving said agitator positioned within a drive meanssection above said reaction section,

(4) sealing means for preventing back-flow of fluid into said drivemeans section, said sealing means comprising:

(a) a disc positioned between said reaction section and said drive meanssection, said disc having its diameter substantially equal to the insidediameter of said autoclave and having a peripheral encircling groovegenerally rectangular in cross section,

(b) a resilient ring seated between the sidewalls of the groove, saidresilient ring having its outer periphery abutting the inner wall ofsaid autoclave, and

(c) an expander ring seated between the sidewalls of the groove, saidexpander ring having its outer periphery abutting the inner periphery ofsaid resilient ring and forming an annular space between its innerperiphery and the inner surface of the groove, sufficient clearancebeing provided between the sidewalls of the groove and the respectiveedges of said resilient ring and said expander ring to permit fluid fromsaid reaction section to fill the annular space, and

(5) means for pressuring said autoclave whereby fluid pressuretransmitted from said reaction section via the clearance and the annularspace urges said resilient ring against the inner wall of said autoclaveto effect sealing contact between the outer periphery of said resilientring and said inner wall.

2. In combination:

(1) an autoclave having a substantially cylindrical, verticallyelongated shell, a removable top head, a reaction section and a motorsection above said reaction section,

(2) an agitator extending along the longitudinal axis of said autoclave,

(3) an agitator motor within a housing positioned within said motorsection,

(4) a sealing ring for preventing back-flow of fluid into the spacebetween the motor housing and the inner surface of said motor section,said sealing ring comprising:

(a) a disc positioned between said reaction section and said motorsection, said disc having its diameter substantially equal to the insidediameter of said autoclave and having at least one peripheral encirclinggroove generally rectangular in cross section,

(b) at least one resilient ring seated between the sidewalls of thegroove, said resilient ring having its outer periphery abutting theinner wall of said autoclave, and

(c) at least one expander ring seated between the sidewalls of thegroove, said expander ring having its outer periphery abutting the innerperiphery of said resilient ring and forming an annular space betweenits inner periphery and the inner surface of the groove, sufllcientclearance being provided between the sidewalls of the groove and therespective edges of said resilient ring and said expander ring to permitfluid from said reaction section to fill the annular space, and

(5) means for pressuring said autoclave whereby fluid pressuretransmitted from said reaction section via the clearance and the annularspace urges said resilient ring against the inner wall of said autoclaveto eifect sealing contact between the outer periphery of said resilientring and said inner wall.

3. In combination:

(1) an autoclave having a substantially cylindrical, verticallyelongated shell, a removable top unit, a reaction section and a motorsection above said reaction section wherein said removable top unitcomprises:

(a) a top head fixedly attached to said shell,

(b) an agitator extending along the longitudinal axis of said autoclave,

(c) an agitator motor within a housing positioned within said motorsection and operably connected to said agitator, the motor housing beingfixedly attached to the inner surface of said top head,

(d) a sealing ring for preventing back-flow of fluid into the spacebetween the motor housing and the inner surface of said motor section,said sealing means com-prising:

(I) a disc positioned between said reaction section and said motorsection, said disc having:

(A) its diameter substantially equal to the inside diameter of saidautoclave,

(B) a recess to receive the lower portion of said motor housing,

(C) a bore extending through the center of the recess to receive saidagitator,

(D) at least one peripheral encircling groove generally rectangular incrosssection,

(E) a plurality of holes through the outer periphery of the recess, and

(F) fastening means passing through the holes to fixedly attach saiddisc to the motor housing,

(II) at least one resilient ring seated between the sidewalls of thegroove, said resilient ring having its outer periphery abutting theinner wall of said autoclave, and

(III) at least one expander ring seated between the sidewalls of thegroove, said expander ring having its outer periphery abutting the innerperiphery of said resilient ring and forming an annular space betweenits inner periphery and the inner surface of the groove, suflicientclearance being provided between the sidewalls of the groove and therespective edges of said resilient ring and said expander ring to permitfluid from said reaction section to fill the annular space, and

(2) means for pressuring said autoclave whereby fluid pressuretransmitted from said reaction section via the clearance and the annularspace urges said resilient ring against the inner wall of said autoclaveto effect sealing contact between the outer periphery of said resilientring and said inner wall.

4. The apparatus of claim 3 wherein said disc comprises a plurality ofperipheral encircling grooves, Wherein said resilient and expander ringsare seated between each of said grooves, and wherein the fluid pressureurges at least the lowermost resilient ring upward against the uppersidewall of at least the lowermost groove and urges at least thelowermost resilient ring radially outward against the inner wall of saidautoclave, normal to its surface thereof.

References Cited UNITED STATES PATENTS 2,897,183 7/1959 Christl 26094.92,964,515 12/1960 Rader 26094.9 2,991,161 7/1961 Gasche 23--29O2,996,363 8/1961 Ruyak 259-l08 X 3,287,092 11/1966 Scudder 23290 ROBERTW. JENKINS, Primary Examiner.

